Method and apparatus for start-spinning a thread on an open-end spinning unit of an open-end spinning machine

ABSTRACT

In order to be able to start-spin on the individual spinning units of an open-end spinning machine under conditions which deviate from the operating conditions and which are, in particular, significantly more favorable for start-spinning, the end of the thread is placed on a ring of fibres located in the spinning rotor at a spinning rotor speed which is reduced relative to the operating speed. At the same time, the sliver feed is reduced in such a manner that the amount of sliver feed corresponds to the reduced speed of the spinning rotor. This reduced sliver speed is produced by a mobile start-spinning unit which is equipped with means which intervene in the drive and/or control of the drive or control means causing feed of the sliver.

The present invention relates to a method for start-spinning a thread onopen-end spinning units of an open-end spinning machine, in which an endof the thread is returned to a spinning rotor, placed on a ring offibres deposited in the spinning rotor and then drawn off again.

It is the object of the present invention to permit neat start-spinningof a thread which is largely independent of the technological conditionsof the open-end spinning unit in the operating condition. It is afurther object of the invention to achieve the technological conditionsfor start spinning independently of the operating condition, withoutnecessitating excessive design and manufacturing effort, whereby,primarily, the sliver feed for the start-spinning operation can bedesigned in such a manner that it corresponds to the speed of thespinning rotor during the start-spinning operation.

According to the present invention, this object is solved in that duringthe placing of the end of the thread on the ring of fibres, the speed ofthe spinning rotor is reduced relative to its operating speed and inthat a mobile start-spinning unit intervenes in the drive and/or controlmeans providing the sliver feed and thus controlling the volume of thering of fibres deposited in the spinning rotor.

This permits the design changes on the individual spinning units to belimited to providing a possibility of intervention for thestart-spinning unit. No other significant changes must be made to theusual drive of the unit for feeding the sliver. The additionalconstructional effort is therefore minimal, thereby permitting themanufacturing costs to be kept low. In an advantageous furtherdevelopment of the invention, for performing the method thestart-spinning unit has an auxiliary drive for the sliver feed, whichcan be coupled with the switched off drive during the start-spinningoperation. By means of this apparatus, it is possible, in a simplemanner, to meter the sliver feed in such a manner that there is asuitable fiber ring in the spinning rotor when the end of the tread isplaced thereon. This utilizes the fact that, normally, during a threadbreak or similar event the feed means of the corresponding open-endspinning unit are practically always interrupted, so that it is merelynecessary to also provide that this drive remains shut off until afterthe start-spinning operation has been performed.

In another embodiment of the invention, the start-spinning unit containsintermittently operating switching means which can be connected with theswitching means of a clutch which is associated to the sliver feed andwhich can be switched on and off. This also requires hardly anyincreased effort, as those elements of the spinning units are generallyemployed which always have to be present. Here, also, it is possible tocontrol the starting characteristic of the sliver feed in a simplemanner by switching it on and off, so that there is a suitable ring offibres in the spinning rotor on which to place the end of the thread,thus providing a perfect start-spinning point.

In a further embodiment of an apparatus according to the presentinvention, the start-spinning unit contains an auxiliary brake which canbe coupled with the means for feeding the sliver. This apparatus alsorequires only very simple modification of the means in the open-endspinning units for feeding the sliver, while the special design of thestart-spinning unit can be kept very simple. There is no difficulty increating a low-wearing auxiliary brake, which ensures the desiredstarting characteristic.

In order, in a further development of the invention, to create anapparatus which operates with very precise timing and with only alimited degree of time lag, the start-spinning unit containsintermittently operating control means which intervene directly from theoutside in trapping means which interrupt the silver feed and whichinterrupt the trapping effect thereof intermittently. Since theswitching means intervene directly in the trapping means, the sliverfeed is switched on and off alternately without any delay for allpractical purposes.

The above discussed and other objects, features and advantages of thepresent invention will become more apparent from the followingdescription thereof, when taken in connection with the accompanyingdrawings, in which

FIG. 1 shows a graphic representation of the starting sequence of aspinning unit with the start-spinning operation indicated therein;

FIG. 2 shows a graphic representation of a reduced sliver feed duringthe starting sequence of a spinning unit;

FIG. 3 shows an apparatus for performing the method according to theinvention, containing an auxiliary drive;

FIGS. 4 and 5 show further apparatuses with auxiliary drives for thesliver feed;

FIGS. 6 to 9 show further embodiments of the invention; and

FIG. 10 shows an embodiment of the invention with switching means actingdirectly on a clamping lever controlling the sliver feed.

Referring now to the drawings, wherein like reference numerals designatelike parts throughout the several views, FIG. 1 shows the spread n of aspinning rotor during time T, in the form of a curve 1, during astarting sequence. The spinning rotor, starting from a standstill,reaches the operating speed, n_(B) at the moment T_(H). It has beenshown that a favourable speed range, in which the start-spinningoperation can be performed most reliably, is located between speeds n₁nn₂, for example. Within this range, it is possible to stipulate astart-spinning point A on curve 1, which then also includesstart-spinning time T_(A) and start-spinning speed n_(A), which isclearly slower than operating speed n_(B).

To perform start-spinning at point A, the end of the thread must bereturned prior to start-spinning time T_(A), for example at time T_(F),indicated on the abscissa, in order for the end of the thread to reachthe ring of fibres deposited in the spinning rotor at time T_(A),whereupon draw-off of the thread is initiated.

The dash-dotted curve 3 also contained in FIG. 1 represents the courseof sliver feed Q through time T. As can be seen from this curve 3, afteronly a short time the sliver feed attains its maximum value Q_(L) attime T_(L). The period of time required therefor is considerably shorterthan the period of time required for the starting sequence of thespinning rotor.

Curves 1 and 3 in FIG. 1 show clearly that at start-spinning time T_(A)the fibre feed is greater than that required by operating conditions,which must result in a change in the quality of the yarn at thestart-spinning point. For this reason, measures must be taken to ensurea suitable ratio between the fibre feed at start-spinning time T_(A) andthe reduced start-spinning speed n_(A) of the spinning rotor. This ispossible, for example, in that the fibre feed is initiated with a delay,so that time T_(L), at which the operating feed quality Q_(L) isattained, is after start-spinning time T₄. Because of the steepness ofcurve 3, the switch-on and start-spinning must be performed at preciselystipulated moments, as the sliver feed conditions change very rapidly.In order to provide a longer period of time for the start-spinningoperation, it is therefore advantageous to provide aids through whichsteepness of curve 3 can be reduced, permitting operating feed Q_(L) tobe attained later.

It would be favourable for the start-spinning operation if curve 3 wereinfluenced in such a manner that it had the same steepness as curve 1. Acurve 4 of this type is illustrated in FIG. 2, which shows feed Q overtime T. A curve 4 of this type for the starting sequence of the feed canbe realized with the present invention.

In many cases, it is sufficient for curve 4 to only be approximated, forexample through a curve 5, shown as a dash-dotted line in FIG. 2. Thelatter possibility is described in detail in the invention of the mainpatent application and can be realized by delayed switch-on of thesliver feed at time T₀, followed by repeatedly switching off the drivebriefly.

With the embodiment according to FIG. 3, both curve 4 as well as curve 5in FIG. 2 can be realized when the sliver feed is started. Provided inthe embodiment shown in FIG. 3 is a start-spinning unit 6, which travelson rails 49 along an open-end spinning machine, of which only onespinning point 7 is illustrated schematically as a cross section.Rotating in an underpressure chamber 8 is a spinning rotor 9, whoseshaft 10 is mounted in bearings 11 in a housing located therebehind.Shaft 10 is driven by means of a tangential belt, whose bottom track 13is pressed against the shaft by a pressure roller 14 in the operationalcondition, while the upper track 12 returns over pressure roller 14. Inthe illustrated brake condition, pressure roller 14 is lifted away fromrotor shaft 10 together with the lower track 13 of the tangential belt,whereby rotor shaft 10 is braked with a brake 15. Brake 15 has anactuating rod 16, which is coupled with a lift-off mechanism 17 forpressure roller 14. Actuating rod 16 of brake 15 can be adjusted bymeans of a double lever 20, which is pivotally mounted about an axle 19.A tension spring 18 acts on double lever 20, said tension spring 18pulling it into a position which releases rotor shaft 10. The free arm21 of double lever 20 extends out of spinning unit 7 to the front.

Fibres are supplied to spinning rotor 9 in a separated state. Toaccomplish this, a sliver is caught by a feed roller 22 and advanced toa separating roller 23, from where the separated fibres reach spinningrotor 9. Feed roller 22 is connected to a toothed belt 27, extending inthe longitudinal direction of the machine, by means of a shaft 24 and agear 25. The connection between gear 25 and feed roller 22 can beinterrupted by means of a solenoid clutch 26, which divides shaft 24.Clutch 26 is electrically connected with a switch 29 of a threadstop-motion 30, which switches off clutch 26 in the event of a threadbreak.

Start-spinning unit 6, which is only illustrated schematically, picks upa thread end 33 from an unillustrated winding cone and returns it to thespinning rotor through a yarn removal channel 32, whereby it is placedon a ring of fibres 31 in the spinning rotor. The thread end 33 isreturned by means of auxiliary draw-off rollers 34 and 35 ofstart-spinning unit 6, of which at least roller 34 can be driven ineither sense of rotation. The thread end is sucked into spinning rotor 9by means of the suction in underpressure chamber 8. The reversal of thesense of rotation of auxiliary draw-off roller 34 is controlled by meansof a thread tension feeler 43 of start-spinning unit 6.

In order to be able to start spinning at a rotor speed which is lowerthan the operating speed, the start-spinning operation is performedduring the starting sequence of spinning rotor 9. To accomplish this,start-spinning unit 6 has an actuating lever 44, which is locatedopposite the free lever arm 21 of double lever 20 of brake 15 whenstart-spinning unit 6 is aligned precisely with the respective spinningunit 7. When free arm 21 of brake 15 is released, which can becontrolled automatically, actuating lever 44 is actuated and, in turn,actuates a starting switch 45, which has a time-lag relay. Startingswitch 45 is connected with a drive motor of auxiliary draw-off rollers34 and 35 for performing the start-spinning operation, on the one hand,and with an auxiliary drive, on the other, through which feed roller 22is driven in such a manner that its starting characteristic, and thusfeed of the sliver, corresponds at least approximately to the startingcharacteristic of the spinning rotor.

In the illustrated embodiment, the auxiliary drive of start-spinningunit 6 has an electric variable-speed motor 75, whose runup can beadjusted by means of a controlling element 76. A wound-rotor motor withappropriate rheostatic starting circuitry or a d.c. motor whose runupcan be otherwise controlled can be provided for this purpose.Variable-speed motor 75 drives a shaft 46, which is connected with adriving wheel 48. Shaft 46 and driving wheel 48 are connected viaadjusting means 74, which permit driving wheel 48 to be shifted axially.Arranged opposite driving wheel 48 is a counterwheel 50, which isrigidly connected with feed roller 22 and which is accessible from theoutside. A gear or friction clutch can be located between driving wheel48 and counterwheel 50.

Since the sliver feed is driven by means of the auxiliary drive ofstart-spinning unit 6 during the start-spinning operation, the maindrive of the sliver feed must remain off during this period, wherebyclutch 26 remains open. This can be controlled by means of an electricaltiming element, for example, which only closes clutch 26 after a delay,even if thread stop-motion 30 has been placed in its operating positionagain, which, in the illustrated embodiment, is performed by means of athread trapper 47 of start-spinning unit 6, which offers the thread endto the opening of the yarn removal channel 32. In this embodiment, itcan be ensured, with the aid of additional switching means ofstart-spinning unit 6, that clutch 26 remains open, so that here, also,the sophistication of the individual spinning units 7 remains small. Forthis purpose, switch 29 of thread stop-motion 30 is designed as a doubleswitch, which can also be switched by a pusher 52 in such a manner thatclutch 26 remains open. The pusher is reversed by means of a lever 53 ofstart-spinning unit 6 associated to it, said lever 53 being switchedwith the aid of an electric servo element. This servo element, and thuslever 53, can be coupled electrically with thread trapper 47, so thatswivelling thread stop-motion 30 into its operating position with theaid of thread trapper 47 results in actuation of pusher 52, so thatclutch 26 remains open. After the start-spinning operation, clutch 26 isclosed, thereby starting the main drive of the sliver feed. In order toavoid mutual damage to the auxiliary drive and the main drive,free-wheeling means are installed in the auxiliary drive. This alsoensures that the transition of the sliver feed from the auxiliary driveto the main drive is uniform and smooth.

It is also possible to actuate the servo element of lever 53 with atiming programme in such a manner as to switch the main drive of feedroller 22 on and off intermittently, which results in astarting-sequence characteristic according to curve 5 in FIG. 2. Thispermits the runup characteristic of the sliver feed to be adapted to therunup characteristic of the spinning rotor in the desired manner,without the employment of an auxiliary drive.

The embodiment shown in FIG. 4 corresponds primarily to the embodimentshown in FIG. 3. In this embodiment, a shaft 24a, extending through themachine in its longitudinal direction, is provided as the main drive fora feed roller 22a; shaft 24a is connected with feed roller 22a by meansof a solenoid clutch 26a. Connected rigidly with feed roller 22a is adrive wheel 50a, to which is associated an auxiliary drive of astart-spinning unit 6a, which can travel along the spinning machine. Theauxiliary drive has a driving wheel 48a, which is pivotally arrangedabout an axle 54 and which is driven by means of a toothed belt 55.Driving wheel 48a can be caused to mesh with drive wheel 50a against theeffect of a spring 57 by means of a solenoid switch 56. Solenoid switch56 is switched, in accordance with FIG. 3, by means of free arm 21 of abrake lever, an actuating lever 44 and a starting switch 45.

Shown in FIG. 5 is an embodiment in which feed rollers 22b of theindividual spinning units 7b are driven by means of a shaft 61,extending through the machine longitudinally, by means of a standingshaft drive 24b. One end of standing shaft 24b has a helical gear 59,which meshes with a corresponding gear 60 of shaft 61. Also mounted onstanding shaft 24b is a further helical gear 58, which meshes with acorresponding gear on feed roller 22b. The standing shaft is dividedbetween helical gears 58 and 59 by means of a solenoid clutch 26. Thissolenoid clutch 26 is switched by a switch 29 of a thread stop-motion 30in a similar manner to that in the embodiment according to FIG. 1.Standing shaft 24b extends beyond helical gear 58, and its free end hasa drive wheel 50b, whose periphery protrudes beyond the enclosure ofspinning unit 7b. Associated to this drive wheel 50b is a driving wheel48b which belongs to an auxiliary drive, containing free-wheeling means51b, of a mobile start-spinning unit 6b. In this embodiment also, inwhich that portion containing feed roller 22b and separating roller 23bcan be swivelled away about an axle 63, the desired startingcharacteristic of the sliver feed can be realized by means of anauxiliary drive controlled by the start-spinning unit. It is ensured, ina manner corresponding to that of FIG. 3, that clutch 26 remains openduring the start-spinning operation.

FIG. 6 shows an embodiment which is similar to that shown in FIG. 4 inwhich a feed roller 22a, which precedes a separating roller 23a, isarranged on a shaft 24a, extending through the machine in thelongitudinal direction thereof, with the aid of a solenoid clutch 26.Feed roller 22a is rigidly connected with a drive wheel 50a, whichbelongs to an auxiliary drive of a start-spinning unit 6a, whichcontains freewheeling means 51a.

FIGS. 7 and 8 show an embodiment of the invention in which one feedroller 22c for each spinning point 7c is arranged on a drive shaft 24c,extending through the machine in the longitudinal direction thereof,with the aid of a slip clutch 64. Slip clutch 64 and feed roller 22c arerigidly connected with a drive wheel 50c, to which is associated adriving wheel 48c of an auxiliary drive of a start-spinning unit 6c,which travels along the spinning machine. This driving wheel 48c ispivotally arranged on an arm in such a manner that it can be meshed withdrive wheel 50c. In this embodiment of the invention, the drive of feedroller 22c is not interrupted, even if there is a thread break. In thisembodiment, the sliver feed is interrupted by trapping sliver 65 with aclamping lever 66, which traps the sliver against an undercasing leverwhich is associated to separating roller 23c. In this connection, it ispossible for the undercasing lever to be able to be moved slightly outof the area of separating roller 23c against the effect of a spring.Trapping is performed by means of a solenoid switch 67, acting onclamping lever 66, said solenoid switch 67 being controlled by switch 29of thread stop-motion 30. In this embodiment, there is an electricallycontrolled actuating member 68 in start-spinning unit 6c, which placesthread stop-motion 30 in the operating position for start spinning, sothat clamping lever 66 releases the sliver feed. In this case, drivingwheel 48c drives drive wheel 50c, and thus feed roller 22c, with thedesired starting characteristic, whereby the required slip is permittedin slip clutch 64. In this embodiment, driving wheel 48c acts as a sortof brake for the main drive in order to achieve the delayed startingcharacteristic. To achieve the same effect, drive wheel 50c or drivingwheel 48c could also be designed as brake discs, for example, which arebraked with metered braking force during the start-spinning operation bybraking means in start-spinning unit 6.

It is also possible to do without delay of the drive of feed roller 22aand, instead, to switch the sliver feed on and off intermittently byintermittently actuating clamping lever 66, which also permits thedesired starting characteristic to be realized. To accomplish this,electrical switching element 68 would have to perform intermittentcontrol movements.

In the embodiment shown in FIG. 9, a feed roller 22d is mounted on aswivel lever 69 which can be pivoted about an axle 73 and which operatesconjointly with an undercasing lever 72. The feed roller is pressedagainst a drive shaft 24d, extending through the machine, by means ofspring force. To interrupt the sliver feed in this embodiment, swivellever 69 is swivelled out, together with an electrical actuating element70, which is also switched by a switch of a thread stop-motion, in sucha manner that feed roller 22d lifts off drive shaft 24d. Arranged on theside of feed roller 22d which is opposite drive shaft 24d is a furtherroller 71, which is connected with a drive wheel 50d. A driving wheel48d of an unillustrated, mobile start-spinning unit is associated tothis drive wheel 50d. In this embodiment, also, feed roller 22d can bedriven by an auxiliary drive of the start-spinning unit during thestart-spinning operation, while the main drive of feed roller 22dremains switched off during this period.

With the embodiment shown in FIG. 10, curve 5 in FIG. 2, especially, canbe realized when the sliver feed is started. Shown in this FIG. 10 is astart-spinning unit 97, which travels along a spinning machine on a rail98 and which is moved to a spinning unit 96 at which a start-spinningoperation is to be performed. The spinning machine is equipped with aplurality of spinning units 96 of this type, arranged one beside theother. Each spinning unit 96 contains a spinning rotor 110, rotating inan underpressure chamber 99, whereby a ring 111 of separated fibres isdeposited continually in spinning rotor 110 and is normally drawn off asthe continuously spun yarn 112 represented by the dash-dotted line inFIG. 10. The yarn is drawn off by means of draw-off rollers 113 and 114and a winding roller 115, which, in the operating condition, is in acontacting relationship with a winding cone 116 which is mounted on anarm 117, which can be pivoted about an axle 118.

Spinning rotor 110 is mounted in two bearings 123 by means of a shaft119. It is driven by a tangential belt 120 121, whose lower track 121 ispressed against shaft 119 by a pressure roller 112 in the operatingcondition. To remedy a thread break, pressure roller 122 is lifted awayfrom shaft 119 with lower track 121, while a brake lining 124simultaneously presses against rotor shaft 119. This situation isrepresented in FIG. 10. Tangential belt 120, 121 is lifted off and brakelining 124 is applied by means of interconnected levers 125 and 126,which can be operated by means of a common actuating lever 129. The freeend 130 of actuating lever 129, which can be pivoted about an axle 128and is loaded in the direction of its operating position by means of atension spring 127, protrudes from the front of spinning unit 96.

The ring 111 of separated fibres continuously deposited in spinningrotor 110 is provided by a sliver 132, which is supplied by a feedroller 131 operating conjointly with a trough 152, to a separatingroller 133, rotating at a considerably higher speed, from where theseparated fibres are supplied to spinning rotor 110 through a fibre feedchannel 134. Feed roller 131 and separating roller 133 are driven byunillustrated drive means. In the event of the thread break, or if thespinning machine is switched off, the supplied sliver 132 is trappedwith a clamping lever 154, whose nose 155 presses against sliver 132 andtraps it on trough 152. This is to avoid clogging spinning rotor 110 andseparating roller 133.

The trapping of sliver 132 is controlled by a thread stop-motion 136,which is arranged at the end of a yarn removal channel 137 and overwhich the spun yarn 112 is advanced. If the thread tension is reduced asa result of a thread break, thread stop-motion 136 assumes the position138 represented by the dashed line. Actuating a switch 135 causesclamping lever 154 to be pressed to the left by means of a liftingmagnet 156 coupled with said switch 135, whereby sliver 132 is trappedby nose 155 of clamping lever 154. This thus interrupts the feed ofsliver 132.

It is the task of start-spinning unit 97, which travels along thespinning machine, to find the broken end 139 of the thread on cone 116in the event of a thread break, and to return it to spinning rotor 110for start-spinning. Start-spinning unit 97 contains a lift-off roller142, with which cone 116 can be lifted off its winding roller 115.Lift-off roller 142 is also driven by the driven draw-off roller 140 ofa pair of draw-off rollers 140, 141, by means of a toothed belt 143.Draw-off roller 140, and thus lift-off roller 142, can be driven ineither sense of rotation. In the illustrated embodiment, lift-off roller142 is mounted about a swivel arm 145, which can be pivoted about theshaft 144 of driven draw-off roller 140. The end 139 of the thread drawnoff by start-spinning unit 97 is led over a thread tension feeler 146,which controls the reversal of the sense of rotation from feed tospinning rotor 110 to draw-off again. Start-spinning unit 97 furthercontains a rotatable thread trapper 149, which offers the end 139 of theyarn to be start-spun again to yarn removal channel 137, through whichthe end of the yarn is then sucked with the aid of an underpressure inrotor chamber 99 in order to be placed on the ring 111 of separatedfibres.

Start-spinning unit 97 is switched on by means of actuating lever 147,which acts on a starting switch 148 equipped with a time-lag relay. Thisstarting switch 148 is electrically coupled with a drive motor ofdraw-off roller 140, on the one hand, and with rotatable thread trapper149 as well as with a switch 150, on the other. By means of a liftingmagnet 151, switch 150 can move the thread stop-motion from itsinoperable position 138 to the right in FIG. 10, beyond its operatingposition 136.

Start-spinning unit 97 operates in the following manner: The initialposition is illustrated in FIG. 10, i.e. rotor shaft 119 is braked,actuating lever 147 rests on the outer end 130 of double lever 129,threaded trapper 149 holds thread 139 to be start spun in theillustrated position, driven rollers 140 and 142 are stopped, and yarnwinding cone 116 is in a contacting relationship with lift-off roller142 and thus no direct contact with spinning unit 96.

After the brake is released, the outer end 130 of double lever 129 movesupward under the effect of tension spring 127. This lowers actuatinglever 125 of brake 124 and the lift-off means for pressure roller 122,on the one hand, i.e. tangential belt 121 presses against rotor shaft119, thereby driving spinning rotor 110. On the other hand, actuatinglever 147 of start-spinning unit 97 is lifted, thereby actuatingstarting switch 148. By means of a time-lag relay or similar meansconnected with said switch 148, both draw-off roller 140 and lift-offroller 142 are driven in such a manner, with simultaneous opening ofthread trapper 149, that thread 139 to be start spun is introduced intoyarn removal channel 137 and further into spinning rotor 110. By meansof switch 150, lifting magnet 151 presses thread stop-motion 138 intoposition 136, i.e. to the right of its operating position, which causesclamping means 154, 155 to not release sliver 132 for the moment. Thisis important, as can be seen by the following. Starting switch 148 alsoactuates a connected changeover switch 157, which is designed as asolenoid switch and which alternately presses clamping means 154 to theright against the resistance of lifting magnet 156 and release it againat preselected times and intervals. This causes nose 155 of clampingelement 154 to lift off sliver 132 intermittently, thereby alternatelystarting and stopping the feed, as feed roller 131 was not switched offand thus constantly rotates. This entire sequence must have occurredbefore spinning rotor 110 has achieved its operating speed. At a given,predetermined tension of thread 139, which has now been start spun,thread tension feeler 146 causes rollers 140 and 142 to reversedirection, which concludes the actual start-spinning operation. Windingroller 116 and thread 139 must then still be returned to spinning unit96 by unillustrated means.

Since lifting magnet 156 must constantly press clamping lever 154 to theleft when switching means 157 switch intermittently, it can be seen thatthread stop-motion 136 must not switch off lifting magnet 156 for thetime being. This is the reason why lifting magnet 151 pressed threadstop-motion 136 to the right of its operating position. After thestart-spinning operation has been completed, lifting magnet 151 releasesthe thread stop-motion, so that said thread stop-motion can assume itsoperating position 136, whereby lifting magnet 156 is switched off andsliver 132 is thereby released again through the effect of anunillustrated spring of clamping lever 154, 155.

Through the present invention, the sluggishness of switch 135, and thusthe coupling with lifting magnet 156, no longer makes any difference, asclamping lever 154 is acted upon directly through intermittentreciprocating-piston switch 157.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It should therefore beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

Having thus fully disclosed our invention, what we claim is: .[.1. Amethod for start-spinning a thread on open-end spinning units of anopen-end spinning machine, in which an end of the thread is returned toa spinning rotor, placed on a ring of fibres deposited in said spinningrotor and then drawn off again, whereby during said placing of said endof the thread on said ring of fibres, the speed of said spinning rotoris reduced relative to its operating speed and whereby a mobilestart-spinning unit intervenes in the drive and/or control of meansproviding the sliver feed and thus controlling the volume of said ringof fibres deposited in said spinning rotor, wherein said thread isreturned to said spinning rotor and placed on said ring of fibres duringacceleration of said spinning rotor from a previously braked conditionto its operating speed..]. .[.2. An apparatus for start-spinning athread on an open-end spinning unit of an open-end spinning machine,having a mobile start-spinning unit with means for returning an end ofthe thread to a spinning rotor, for placing said end of the thread on aring of fibres located in said spinning rotor and for drawing off thestart-spun thread again, as well as means for reducing the speed of saidspinning rotor relative to its operating speed, and means whichintervene in one of drive means and control means providing the feed ofthe sliver forming said fibre ring for the purpose of reducing the rateof said formation of said fibre ring, wherein a common mechanical drivemeans is provided for rotatably driving spinning rotors of a pluralityof said spinning units, and wherein said means which intervene includemeans for interrupting the rotatable drive of one of said spinningrotors without interrupting the rotatable drive of the other of saidcommonly driven spinning rotors..]. .[.3. An apparatus forstart-spinning a thread on an open-end spinning unit of an open-endspinning machine, having a mobile start-spinning unit with means forreturning an end of the thread to a spinning rotor, for placing said endof the thread on a ring of fibres located in said spinning rotor and fordrawing off the start-spun thread again, as well as means for reducingthe speed of said spinning rotor relative to its operating speed, andmeans which intervene in one of drive means and control means providingthe feed of the sliver forming said fibre ring for the purpose ofreducing the rate of said formation of said fibre ring, wherein saidmeans for placing said end of the thread and said means for reducing thespeed of said spinning rotor relative to its operating speed areconstructed and synchronized such that said thread is returned to saidspinning rotor and placed on said ring of fibres during acceleration ofsaid spinning rotor from a previously braked condition to its operatingspeed..].
 4. An apparatus for start-spinning a thread on an open-endspinning unit of an openend spinning machine, having amobilestart-spinning unit with means for returning an end of the thread to aspinning rotor, for placing said end of the thread on a ring of fibreslocated in said spinning rotor and for drawing off the start-spun threadagain, as well as means for reducing the speed of said spinning rotorrelative to its operating speed, and means which intervene in drivemeans providing the feed of the sliver forming said fibre ring for thepurpose of reducing the rate of said formation of said fibre ring, inwhich said start-spinning unit contains a driving wheel which, throughadjustment, can be coupled with a corresponding drive wheel of the drivemeans associated to the open-end spinning unit for the feed of saidsliver.
 5. The apparatus according to claim 4, in which said drive wheelis arranged on a standing shaft which drives a feed roller for feedingthe sliver by means of helical gears.
 6. An apparatus for start-spinninga thread on an open-end spinning unit of an openend spinning machine,having a mobile start-spinning unit with means for returning an end ofthe thread to a spinning rotor, for placing said end of the thread on aring of fibres located in said spinning rotor and for drawing off thestart-spun thread again, as well as means for reducing the speed of saidspinning rotor relative to its operating speed, and means whichintervene in drive means providing the feed of the sliver forming saidfibre ring for the purpose of reducing the rate of said formation ofsaid fibre ring, in which an auxiliary drive of the start-spinning unithas freewheeling means.
 7. An apparatus for start-spinning a thread onan open-end spinning unit of an open-end spinning machine, having amobile start-spinning unit with means for returning an end of the threadto a spinning rotor, for placing said end of the thread on a ring offibres located in said spinning rotor and for drawing off the start-spunthread again, as well as means for reducing the speed of said spinningrotor relative to its operating speed, and means which intervene incontrol means providing the feed of the sliver forming said fibre ringfor the purpose of reducing the rate of said formation of said fibrering, in which, through transmission means of the start-spinning unit, athread stop-motion connected with a reversing switch is caused tointerrupt a stationary drive for feeding the sliver.
 8. An apparatus forstart-spinning a thread on an open-end spinning unit of an open-endspinning machine, having a mobile start-spinning unit with means forreturning an end of the thread to a spinning rotor, for placing said endof the thread on a ring of fibres located in said spinning rotor and fordrawing off the start-spun thread again, as well as means for reducingthe speed of said spinning rotor relative to its operating speed, andmeans which intervene in drive means providing the feed of the sliverforming said fibre ring for the purpose of reducing the rate of saidformation of said fibre ring, in which the sliver is fed by means of afeed roller, which, under normal operating conditions, is pressedagainst a drive shaft extending over a plurality of spinning units andwhich, in the event of a thread break, is lifted off the drive shaft byan actuating element which is electrically connected with a threadstop-motion, and is pressed against a roller which is driven by adriving wheel of the start-spinning unit.
 9. The apparatus according toclaim 8, in which said feed roller is associated to a trough which trapsthe sliver, said trough performing the swivel movement of the feedroller. .[.10. An apparatus for start-spinning a thread on an open-endspinning unit of an open-end spinning machine, having a mobilestart-spinning unit with means for returning an end of the thread to aspinning rotor, for placing said end of the thread on a ring of fibreslocated in said spinning rotor and for drawing off the start-spun threadagain, as well as means for reducing the speed of said spinning rotorrelative to its operating speed, and means which intervene in controlmeans providing the feed of the sliver forming said fibre ring for thepurpose of reducing the rate of said formation of said fibre ring, inwhich the start-spinning unit contains intermittently operatingswitching means which can be connected with the switching means of aclutch which is associated to the sliver feed and which can be switchedon and off..]. An apparatus for start-spinning a thread on an open-endspinning unit of an open-end spinning machine, having a mobilestart-spinning unit with means for returning an end of the thread to aspinning rotor, for placing said end of the thread on a ring of fibreslocated in said spinning rotor and for drawing off the start-spun threadagain, as well as means for reducing the speed of said spinning rotorrelative to its operating speed, and means which intervene in controlmeans providing the feed of the sliver forming said fibre ring for thepurpose of reducing the rate of said formation of said fibre ring, inwhich said start-spinning unit contains switching means which can becoupled to trapping means, associated to each spinning unit, forinterrupting the sliver feed, said switching means permitting saidtrapping means to be switched either on or alternatively on and off atpredetermined time.
 12. An apparatus for start-spinning a thread on anopen-end spinning unit of an open-end spinning machine, having a mobilestart-spinning unit with means for returning an end of the thread to aspinning rotor, for placing said end of the thread on a ring or fibreslocated in said spinning rotor and for drawing off the start-spun threadagain, as well as means for reducing the speed of said spinning rotorrelative to its operating speed, and means which intervene in drivemeans providing the feed of the sliver forming said fibre ring for thepurpose of reducing the rate of said formation of said fibre ring, inwhich said start-spinning unit contains an auxiliary brake which can becoupled with the means for feeding the sliver.
 13. The apparatusaccording to claim 12, in which a known feed roller is provided forfeeding the sliver, said roller being able to be coupled with saidauxiliary brake by means of a slip clutch arranged on a shaft extendingover a plurality of spinning units and by means of a gear.
 14. Anapparatus for start-spinning a thread on an open-end spinning unit of anopen-end spinning machine, having a mobile start-spinning unit withmeans for returning an end of the thread to a spinning rotor, forplacing said end of the thread on a ring of fibres located in saidspinning rotor and for drawing off the start-spun thread again, as wellas means for reducing the speed of said spinning rotor relative to itsoperating speed, and means which intervene in control means providingthe feed of the sliver forming said fibre ring for the purpose ofreducing the rate of said formation of said fibre ring, in which saidstart-spinning unit contains intermittently operating switching meanswhich intervene directly from the outside in trapping means whichinterrupt the sliver feed and which intermittently interrupt saidtrapping effect.
 15. The apparatus according to claim 14, in which eachopen-end spinning unit is equipped with a thread tension feelercontrolling the actuation of the trapping means, whereby adjusting meansof the start-spinning unit are associated to said feeler, said adjustingmeans placing said feeler, during the start-spinning operation, in aposition extending beyond the operating position, in which said trappingmeans remain switched on.
 16. The apparatus according to claim 15, inwhich each open-end spinning unit contains a clamping lever which trapsthe sliver in a trough, which can be loaded in the clamping directionwith an adjusting member, opposite which an adjusting member of thestart-spinning unit is arranged on the clamping lever and alignedoppositely, said latter adjusting member being dimensioned significantlystronger. .[.17. A method for start-spinning a thread on an open-endspinning unit of an open-end spinning machine, comprising:reducing thespeed of a spinning rotor of said spinning unit to a speed below itsoperational spinning speed, intervening in at least one of the drive andcontrol of sliver feed means of said spinning unit so as to control thevolume of fibres deposited by said sliver feed in said spinning rotor,placing an end of a thread piece on a ring of fibres deposited in saidspinning rotor and drawing said thread piece out of said spinning rotorupon connection of said end with said fibres, and controlling the speedof said rotor and the timing of said intervening step such that therotor is accelerating toward said operational spinning speed during saidplacing step..].
 18. A method .[.according to claim 17,.]. .Iadd.forstart-spinning a thread on an open-end spinning unit of an open-endspinning machine, comprising:reducing the speed of a spinning rotor ofsaid spinning unit to a speed below its operational spinning speed,intervening in at least one of the drive and control of sliver feedmeans of said spinning unit so as to control the volume of fibresdeposited by said sliver feed in said spinning rotor, placing an end ofa thread piece on a ring of fibres deposited in said spinning rotor anddrawing said thread piece out of said spinning rotor upon connection ofsaid end with said fibres, and controlling the speed of said rotor andthe timing of said intervening step such that the rotor is acceleratingtoward said operational spinning speed during said placing step,.Iaddend. wherein said step of controlling the speed of said rotor andthe timing of said intervening step includes rotatably driving saidrotor by auxiliary driving means that are separate from main drive meansthat normally drive said rotor at its operational spinning speed.
 19. Amethod according to claim 18, wherein said spinning unit is one of aplurality of spinning units having respective spinning rotors driven bya common main drive means, and wherein said controlling the speed ofsaid rotor and the timing of said intervening step includes interruptingthe drive connection between said main drive means and one of saidspinning rotors without interrupting the drive connection of other ofsaid spinning rotors and said main drive means. .[.20. An apparatus forstart-spinning a thread on an open-end spinning unit of an open-endspinning machine, said apparatus comprising:reducing means for reducingthe speed of a spinning rotor of said spinning unit to a speed below itsoperational spinning speed, intervening means for intervening in atleast one of the drive and control of sliver feed means of said spinningunit so as to control the volume of fibres deposited by said sliver feedin said spinning rotor, placing means for placing an end of a threadpiece on a ring of fibres deposited in said spinning rotor and drawingsaid thread piece out of said spinning rotor upon connection of said endwith said fibres, and controlling means for controlling the speed ofsaid rotor and the timing of said intervening step such that the rotoris accelerating toward said operational spinning speed during saidplacing by said placing means..].
 21. .[.An apparatus according to claim20,.]. .Iadd.An apparatus for start-spinning a thread on an open-endspinning unit of an open-end spinning machine, said apparatuscomprising:reducing means for reducing the speed of a spinning rotor ofsaid spinning unit to a speed below its operational spinning speed,intervening means for intervening in at least one of the drive andcontrol of sliver feed means of said spinning unit so as to control thevolume of fibres deposited by said sliver feed in said spinning rotor,placing means for placing an end of a thread piece on a ring of fibresdeposited in said spinning rotor drawing said thread piece out of saidspinning rotor upon connection of said end with said fibres, andcontrolling means for controlling the speed of said rotor and the timingof said intervening step such that the rotor is accelerating toward saidoperational spinning speed during said placing by said placing means,.Iaddend. wherein said control means includes means for rotatablydriving said rotor by auxiliary driving means that are separate frommain drive means that normally drive said rotor at its operationalspinning speed. .[.22. Apparatus according to claim 20, wherein saidspinning unit is one of a plurality of spinning units having respectivespinning rotors driven by a common main drive means, and wherein saidcontrol means includes means for interrupting the drive connectionbetween said main drive means and one of said spinning rotors withoutinterrupting the drive connection of other of said spinning rotors andsaid main drive means..]. .[.23. Apparatus according to claim 20,wherein said reducing means, intervening means, placing means, andcontrolling means are carried on a mobile unit which is mounted formovement along a plurality of spinning units..].